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  1. hevans1944

    Obsolete Dual Diode Specs

    I also spent about an hour searching the web for these with nary a result. Is all you have are "a few of these" and zero prospects of replacing them with a more modern equivalent? If so, I would cut the leads off flush with the case and then crush the epoxy package in a large bench vice before...
  2. hevans1944

    12V and 5v(USB) battery pack build. help.

    Gee, are those available now here in the USA? Can I get one with an autopilot so I can snooze while it moovze? I would rather have a Kia Turbo Sport, but mebbe Chinee be all better, huh?
  3. hevans1944

    AC Laptop Adapter -> How to make 19v output into 5v?

    If you have some power (a few watts) to spare, a circuit could be designed that accepted 19 V DC and produced 5 V DC at a current limited by the available input power, not the maximum output current. So, assuming the maximum power is 90 watts delivered at 19 volts, then you should be able to...
  4. hevans1944

    Wi-Fi Beacon Photo or Plot?

    Looks like your education is coming along nicely. The Beacon is just one indication that a rabbit-hole exists. Now you must buy (or build) hardware that will inspect ALL the packets streaming through your Access Point and decide what to do with them. This is essentially what a firewall does...
  5. hevans1944

    Wi-Fi Beacon Photo or Plot?

    I am sure we have "lost" you since you seem to have absolutely no idea what "the actual Wi-Fi signal" is. Why don't you get up to speed on modern communications theory and modulation methods before wasting our time here in this forum? Here is a Wi-Fi Primer (a beginners text) from Texas...
  6. hevans1944

    Trying to make a circuit diagram from this

    Seems we have all been down this road with this poster. Not worth to time to respond.
  7. hevans1944

    Video signal amplifier.

    This thread has wandered way off the original topic, which involved attempting to transmit composite (presumably NTSC or PAL) video a long distance, five hundred feet, using ordinary shielded four-conductor instrumentation cable wound up on a six-inch diameter reel, said signal to be boosted by...
  8. hevans1944

    Confusion about led's forward voltage

    As @thedoc298 said, each LED is different. It used to be that you could predict the forward voltage by the color of light the LED emitted. This is certainly NOT true for "white light" LEDs, which use a wavelength-converting phosphor to emit light of a different color than the LED illuminating...
  9. hevans1944

    restoring old garage door opener-receiver/transmitter

    Here is a side note that may or may not interest you. I bought my first house in Dayton, Ohio, about thirty-something years ago. It came with a detached two-car garage and an automatic garage door opener. The door opener was based on a tone-encoded Citizens Band transmitter and, IIRC, a vacuum...
  10. hevans1944

    restoring old garage door opener-receiver/transmitter

    Yes it does. It means the low-voltage circuit that controls the door lifting/lowering motorized mechanism is completely independent of the ancient Heathkit receiver. You can ignore the antique receiver and add your own transmitter/receiver pair to perform the function of pressing the button on...
  11. hevans1944

    filtering a 3000V power supply output.

    I think transient surge suppressors will not work in your application. It is my understanding that once their threshold voltage is "triggered" they become low-impedance "shorts" to absorb the energy surge that led to the over-voltage condition. How often, and how long, this short-circuit can...
  12. hevans1944

    restoring old garage door opener-receiver/transmitter

    Your answer to @Bluejets question in post #14 is important! How do you operate your garage door now? Or has the door been mechanically disconnected from the door-lifting mechanism, so you open and close it manually?
  13. hevans1944

    Capacitance measurements and frequency

    Cite some of those "various research papers" you have come across. Capacitive reactance varies with frequency, capacitance not so much. Tell us what you are trying to DO, please. No half-baked ideas of how to do it, nor off-the-wall statements about how capacitance varies as a function of...
  14. hevans1944

    Are UJT's used anymore?

    UJTs may not be exactly obsolete, but they have had their "day in the sun" as far as popularity goes. IIRC, their main function was to establish timing pulses for triggering SCRs in so-called phase-controlled dimmer circuits. They also were used to make simple oscillators covering the audio...
  15. hevans1944

    junior project at university

    My first advice would be to ask a moderator to move this thread to the Homework Forum. My second advice would be to ask you to define your project in sufficient detail such that a design to construct the project is feasible. We can perhaps then begin to offer you some suggestions, advice, and...
  16. hevans1944

    AC Polarity swapping circuit

    So, let's get to the meat of WHY @m_alizd, Matt, with almost NO knowledge of what his "polarity inverted" AC wave forms will actually DO when applied to a load of some sort, is trying to design-to-cost (worrying about nickles and dimes as @WHONOES has intimated in his post #21) instead of...
  17. hevans1944

    electronic load

    Yeah, I probably could have figured that out from the content of this thread, but I just wanted to be sure, since your question was juxtaposed right after a comment I made in post #38. @tasty has avoided answering any questions that would have required the use of an oscilloscope to find an...
  18. hevans1944

    electronic load

    . Are you asking me or @tasty? If I had more time, I would purchase a handful of MOSFETs and try to duplicate the failure modes seen by @tasty. I have a lot of experience blowing parts up, all from my earlier years as an electronics bench technician. As I became more experienced, I destroyed...
  19. hevans1944

    electronic load

    Agreed it is a much better package for heavier power dissipation. I just thought it was a huge departure from the TO-220 and TO-247 packages, but it probably doesn't make any difference since no one can agree on what's wrong, much less offer a troubleshooting procedure to correct it. Where is...
  20. hevans1944

    electronic load

    Did you perhaps mean a TO247 package instead of TO227? And, BTW, where does the DUT connect? Between the Vcc supply and the MOSFET drains or somewhere else? Sorry, I somehow missed your schematic of the op-amp negative feedback driving the MOSFET gate, based on the voltage drop across the...
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